Method of and apparatus for cleaning ink jet head

- Fujitsu Limited

Disclosed are a method of and an apparatus for cleaning a plurality of nozzles of an ink jet head. This cleaning method comprises a step of covering a nozzle surface formed with the plurality of nozzles with a cap; a step of depressurizing an air space formed between the nozzle surface and the cap by use of a depressurizing element to suck the inks from the nozzles; a step of stopping the depressurization by the depressurizing element; a step of keeping the nozzle surface covered with the cap so that the inks jetted from the nozzles due to the depressurization wet-spread over the entire nozzle surface by a capillary force; and a step of retracting the cap from the nozzle surface. Further, in this cleaning apparatus, a contact angle .theta.1 between the ink and the cap internal surface and a contact angle .theta.2 between the ink and the nozzle surface are set to 90.degree. or smaller and also set such that .theta.2 is not greater than .theta.1.

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Claims

1. A method of cleaning an ink jet head having a plurality of nozzles for effecting a record by jetting ink from openings in the ends of said nozzles onto a recording medium, said method comprising the steps of:

covering a nozzle surface containing the ends of said plurality of nozzles of said ink jet head with a cap to form an air space between said nozzle surface and said cap and closed to the exterior thereof;
depressurizing said air space by use of depressurizing means to suck ink from said nozzles into said air space;
stopping the depressurization by said depressurizing means upon achieving a predetermined negative pressure condition in said air space;
keeping the nozzle surface covered by said cap closed to the exterior thereof while maintaining a depressurized state in said air space for a period of time so that the ink extracted from said nozzles due to the depressurization wet-spreads over the entire nozzle surface by a capillary force to immerse said openings of said nozzles and dissolve deposited or solidified solutes therein; and
thereafter, retracting said cap from the nozzle surface.

2. A method of cleaning an ink jet head according to claim 1, wherein said depressurizing step is a step of producing a reduced pressure equal to or smaller than 1-(S.multidot.L/V) where S is the area of the nozzle surface including all said plurality of nozzles, L is the average spacing between the region of the nozzle surface and the cap internal surface bearing a face-to-face relationship with said region, and V is the intra-cap capacity when said plurality of nozzles are covered with said cap.

3. A method of cleaning an ink jet head according to claim 1, wherein said nozzle surface is kept covered by said cap and closed to the exterior thereof until a pressure within the air space reaches atmospheric pressure.

4. A method of cleaning an ink jet head according to claim 2, wherein said nozzle surface is kept covered by said cap and closed to the exterior thereof until a pressure within the air space reaches atmospheric pressure.

5. A method of cleaning an ink jet head according to claim 1, wherein said nozzle surface is kept covered by said cap and closed to the exterior thereof until a predetermined holding time elapses after pressure within the air space has reached atmospheric pressure.

6. A method of cleaning an ink jet head according to claim 2, wherein said nozzle surface is kept covered by said cap and closed to the exterior thereof until a predetermined holding time elapses after a pressure within the air space has reached atmospheric pressure.

7. A method of cleaning an ink jet head according to claim 1, further comprising a step of repeating said steps starting with said step of covering the nozzle surface with said cap when clogging in said nozzles on the nozzle surface is not removed.

8. A method of cleaning an ink jet head according to claim 7, wherein said repeating step includes a step of gradually enhancing the reduced pressure by said depressurizing means in said depressurizing step.

9. A method of cleaning an ink jet head according to claim 6, further comprising a step of repeating said steps starting with said step of covering the nozzle surface with said cap when clogging in said nozzles on the nozzle surface is not removed, said repeating step including a step of gradually increasing die holding time in said keeping step.

10. An apparatus for cleaning an ink jet head having a plurality of nozzles defining a nozzle surface containing nozzles having openings for effecting a record by jetting out ink on a recording medium, said apparatus comprising:

a cap for covering said nozzle surface to form an air space between said nozzle surface and said cap and closed to the exterior thereof;
depressurizing means communicating with said air space for depressurizing said air space to suck ink from said nozzle openings; and
means for maintaining a depressurized state in said air space following termination of operation of the depressurizing means and while said air space is closed to the exterior thereof at least until said air space contains ink sufficient to cover the openings of said plurality of nozzles for a period of time sufficient to dissolve deposited or solidified solutes therein,
wherein a contact angle.theta.1 between the ink and the cap internal surface and a contact angle.theta.2 between the ink and the nozzle surface are set to 90.degree. or smaller and also set as.theta.2 is not greater than.theta.1.

11. An apparatus for cleaning an ink jet head according to claim 10, wherein the nozzle surface and an internal surface of the cap are formed so that the contact angel.theta.1 and the contact angle.theta.2 are set to 90.degree. or smaller and also set such that.theta.2 is not greater than.theta.1.

12. An apparatus for cleaning an ink jet head according to claim 10, wherein the ink has a composition producing a contact angle.theta.1 and a contact angle.theta.2 set to 90.degree. or smaller and also set such that.theta.2 is not greater than.theta.1.

13. An apparatus for cleaning an ink jet head according to claim 10, wherein said cap is provided in a face-to-face-position with the nozzle surface with respect to the cap internal surface and further includes a member for narrowing a spacing between the cap internal surface and the nozzle surface.

14. An apparatus for cleaning an ink jet head according to claim 10, wherein said cap has a closed surface bearing a face-to-face relationship with the nozzle surface.

15. An apparatus for cleaning an ink jet head according to claim 10, wherein said ink jet head includes a surface peripheral to the nozzle surface that produces a contact angle different from that produced on the nozzle surface on which said plurality of nozzles are arranged.

16. An apparatus for cleaning an ink jet head according to claim 10, further comprising:

pressure detecting means for detecting a pressure in said air space within said cap; and
a control circuit for controlling said depressurizing means in accordance with a detected output of said pressure detecting means.

17. An apparatus for cleaning an ink jet head having a plurality of nozzles for effecting a record by jetting ink from openings in the ends of said nozzles onto a recording medium, said apparatus comprising:

a cap for covering a nozzle surface containing said nozzle openings to form an air space between said nozzle surface and said cap and closed to the exterior thereof;
depressurizing means communicating with said air space for depressurizing said air space to suck ink from said nozzles;
a cap operating mechanism for closely fitting said cap to the nozzle surface and retracting said cap therefrom;
means for maintaining said air space closed and depressurized following termination of operation of the depressurizing means; and
a control circuit operative to control said cap operating mechanism and said depressurizing means, said control circuit including means for closely fitting said cap to the nozzle surface to form said air space, means for operating said depressurizing means after said cap is fitted to said nozzle surface for a limited period of time sufficient to provide a predetermined negative pressure within said air space and then to stop operation of said depressurizing means, means operative to maintain said cap fitted to the nozzle surface and closed to the exterior of said cap to enable the negative pressure in the air space to extract ink from said nozzles and to wet-spread over the nozzle surface to immerse the nozzle openings by dint of capillary force whereby solutes deposited or solidified in said nozzles are dissolved, and means for retracting said cap from the nozzle surface.

18. An apparatus for cleaning an ink jet head according to claim 17, wherein said control circuit controls said depressurizing means to give a reduced pressure equal to or smaller than 1-(S.multidot.L/V) where S is the area of the nozzle surface including all said plurality of nozzles, L is the average spacing between this region and the cap internal surface bearing a face-to-face relationship with this region, and V is the intra-cap capacity when said plurality of nozzles are covered with said cap.

19. An apparatus for cleaning an ink jet head according to claim 17, wherein said control circuit controls said cap operating mechanism to cover the nozzle surface with said cap and to maintain it closed to the exterior thereof until the pressure within the air space reaches atmospheric pressure.

20. An apparatus for cleaning an ink jet head according to claim 17, wherein said control circuit controls said cap operating mechanism to cover the nozzle surface with said cap and to maintain it closed to the exterior thereof until a predetermined holding time elapses after a pressure within the air space has reached atmospheric pressure.

21. An apparatus for cleaning an ink jet head according to claim 17, further comprising pressure detecting means for detecting a pressure in the air space within said cap,

said control circuit controlling said depressurizing means in accordance with a detected output of said pressure detecting means.

22. An apparatus for cleaning an ink jet head according to claim 17, further comprising pressure detecting means for detecting a pressure in the air space within said cap,

said control circuit controlling said depressurizing means and said cap operating mechanism in accordance with a detected output of said pressure detecting means.

23. An apparatus for cleaning an ink jet head according to claim 17, wherein a contact angle.theta.1 between the ink and the cap internal surface and a contact angle.theta.2 between the ink and the nozzle surface are set to 90.degree. or smaller and also set such as.theta.2 is not greater than.theta.1.

Referenced Cited
U.S. Patent Documents
4739340 April 19, 1988 Terasawa
4825231 April 25, 1989 Nozaki
4952947 August 28, 1990 Kyoshima
5027134 June 25, 1991 Harmon et al.
5128690 July 7, 1992 Nozawa
5164748 November 17, 1992 Katayanagi et al.
5248999 September 28, 1993 Mochizuki et al.
5389961 February 14, 1995 Takagi
5570116 October 29, 1996 Soga
Foreign Patent Documents
0 423 475 A1 April 1991 EPX
0 465 260 A2 January 1992 EPX
0 465 260 A3 January 1992 EPX
55-107481 August 1980 JPX
59-162057 September 1984 JPX
2-283455 November 1990 JPX
4-259564 September 1992 JPX
Other references
  • Prior Art Information List; Dated Jul. 25, 1995; Search Report w/3 cited documents; (1) Publication No.: JP4219250; Publication Date: Aug. 10, 1992, (2) Publication No.: JP4014461; Publication Date: May 8, 1990, (3) Publication No.: JP4235053; Publication Date: Jan. 9, 1991. Communication-European Search Report; Aplication No.: 95302670.5; Jul. 11, 1995.
Patent History
Patent number: 5784081
Type: Grant
Filed: Mar 23, 1995
Date of Patent: Jul 21, 1998
Assignee: Fujitsu Limited (Kanagawa)
Inventors: Mitsuo Ozaki (Kawasaki), Shigeharu Suzuki (Kawasaki), Shino Sakai (Kawasaki), Keita Akeno (Kawasaki), Shigeyoshi Umemiya (Kawasaki), Yasuo Yamagishi (Kawasaki)
Primary Examiner: David M. Gray
Assistant Examiner: Michael Dalakis
Law Firm: Armstrong, Westerman, Hattori, McLeland & Naughton
Application Number: 8/409,094
Classifications
Current U.S. Class: Suction (347/30); Movement (347/32)
International Classification: B41J 2165;